The Canadian Food Inspection Agency (CFIA) is asking home gardeners to throw out all fall purchased mums and to report any cases of CWR seen to a CFIA Office. Contact information for CFIA offices is available at http://inspection.gc.ca/english/directory/offbure.shtml#w-o. CFIA has sent brochures on CWR to garden centers for display and distribution to the public. 
The following Canada NewsWire release gives more details. It is available online at (www.newswire.ca/releases/November2001/20/c9179.html)

OTTAWA, Nov. 20 /CNW/ - The Canadian Food Inspection Agency (CFIA) is asking home gardeners for help in eradicating a serious disease of chrysanthemums. For the first time, chrysanthemum white rust (CWR) has been found in the British Columbia commercial chrysanthemum industry and efforts are being made to trace the origins of the outbreak. The disease could have severe trade and economic implications for our commercial chrysanthemum growers. 
In early October, CWR was found in several commercial chrysanthemum greenhouses. Following initial discovery of the diseased plants, the CFIA issued quarantine notices and placed destruction orders on infected plants. Traceback of movement of plants and cuttings is currently underway to reduce the possible risk of transmission.
While these greenhouses have been quarantined, a large portion of the crop had already been sold. The CFIA is asking for the public's help in eradicating the disease.
The first symptoms of white rust are whitish-yellow circular spots on the upper leaf surface. They vary in size from pinhead size to five millimeters across. As the infection develops, the spot becomes sunken and a whitish or buff-coloured pustule appears on the under surface of the leaf. 
The disease survives inside the plant, so if a chrysanthemum with CWR over-winters in the garden, it can spread the disease next fall to other chrysanthemums in your garden and surrounding gardens or to commercial growers. It is also possible that other chrysanthemums in the garden have already been infected. Symptoms are not always obvious in the early stages of infection.
To aid in the eradication of this disease, the CFIA is asking those who have purchased a potted mum this fall not to plant it in your garden. Instead, once you have finished enjoying it, dispose of it with your household garbage.
Do not compost the plants in your backyard composter. If you planted them in your garden, it is recommended that you pull out the purchased chrysanthemum plus any other chrysanthemums in your garden as a precaution. The disease spreads very quickly and easily from one chrysanthemum to another.
CWR affects twelve species of chrysanthemums including potted florist mums, cut mums and garden mums. It does not affect people or pets, nor does it affect any plants outside of the plant groups of Chrysanthemum, Dendranthema, and Leucanthemella. It will not affect your marguerite, painted or shasta daisies.
Both Canada and the United States are trying to prevent the disease from becoming established in North America. When growers have CWR they must destroy all affected plant material at their expense and are not allowed to ship any chrysanthemums until their operation is determined to be free of CWR.

More information on the disease and colour photographs can be found on the CFIA Web site, located at: www.inspection.gc.ca/english/ppc/science/pps/datasheets/puchore.shtml For further information: Ken Wong, Program Officer, Canadian Food Inspection Agency, (604) 666-0974. 

There is other information on CWR at: 

http://www.gov.bc.ca/agf/
http://www.pestalert.org/pestnews.cfm
http://www.ufgca.com/pr-1.html
http://www.agf.gov.bc.ca/croplive/cropprot/cwrust.htm

The concern is that some infected potted mums were distributed before the disease was detected. With our mild winters, the infected plants will usually survive and would remain symptomless until late August. This creates the potential for the disease to establish in someone's garden--a serious problem for them, and obviously for commercial growers and the CFIA as well. We want to be free of this disease. California has been having problems eradicating the disease because of these reservoirs in home gardens. We do not want that situation here. 

Leslie MacDonald, P.Ag. 
Plant Pathologist 
BC Ministry of Agriculture, Food & Fisheries 
1767 Angus Campbell Rd., Abbotsford, B.C. 
Canada V3G 2M3 
604.556-3029 (fax) 556-3030

Leslie.MacDonald@gems3.gov.bc.ca